Polymerization of butadiene-1,3 hydrocarbons



- Patented July 31, 1945 .wotmrmzmou or BU'rAnmha-La v nrnaocanaons Waldo L. Semon, Silver Lake, Ohio, assignor, Goodri assignments, to The Ohio, a corporation of New mesne Company, Akron, York I I v No Drawing.

a, method whereby butadiene-Lshydrocarbons maybe polymerized in aqueous emulsion "to form products closely resembling natural crude rubber.

The emulsion polymerization of butadiene-1,3 hydrocarbons either alone orin-admixture with other monomers copolymerizable therewith to form compositions of matter more or less resembling rubber is well known. It has been commonly observed. however, that the products ofsuch ized rubber rather than natural crude rubber in respect to solubility, plasticity, and processing characteristics. Thus it" has" often been found that the polymers were insoluble in. and, in some cases, not even swelled by benzene or acetone, and that they were tough, non-plastic materials which either would not homogenizeon a mill or which were very difilcu'lt to mill and'to subject to other ordinary processing operations.

I have now discovered a which modifiesthe emulsionpolymerization oi butadiene-Liihydrocarbons'in such a manner that polymers more nearly resembling natural crude rubbermay beproduced than when the polymerization reactions oiten.,r esemble vulcanclass -oi materials polymerization is effected in the absence of the 7 materials of. this invention. :ThisclaSs oi materials. which -I .have termed modifiers." consists of compounds containing the group I I s x s I II II x- -s-c-s-c -xwherein X represents oxygen or sulfur. Corn poundscontaining this group may be readily prepared by the reaction of an alkali metal xanthate with thiophosgene as disclosed'by Willcox, J. A.

C. S. 28, 1033 (11906). The 'xanthatemay be de-. rived from an alcohol'ora thiolsuch asethanol,'

allyi alcohol, cyclohexyl 'alco'hol, .tetrahydroturturyl alcohoLbenzyl alcohol, isbpropyl 'mercaptan,

etc..by' a reaction. with carbon disulfide and-an alkali in'known manners. The bis(alkoxythiono) tritmocarbonfltes such as bis(ethoxythiono) trithlocarbonate,. bis(isopropoxythiono) trithiocarbonate, and bis(ter. butoxythiono) ,trithiocarbonate. are a preferred class of compounds because or their comparatively low cost and the ease with which they may be prepared. but any other compounds containing the group may be employed if desired. suchasthe dithiovantageous to employ a types of modifiers such as presence of about The p oportion I 'cluded in the compositiondepends somewhat by ch Application September 22, 1941, Serial No. 411,849

8Claims.. (c1. zoo-84.5

- This invention relates to the polymerization of butadiene-Lfi hydrocarbons, and particularly to' carbonates'prepared by reacting a xanthate and phosgene.

As a specific example of this invention; amix ture of 55 parts by weightoi butadiene and 45 parts of acrylonitrile was agitated at 30 C; in'the.

250 parts of an aqueous solution of myristic acid which had been 85%.neutralized with sodium hydroxide, 0:35 partiofhydrogen peroxide as an initiator,0.1'partotsodium ferri phosphate as a catalyst, and 0.7 part of. bis- (isopropoxythiono) ti'ithiocarbonate. A synthetic rubber 'iatex was obtained in a nearlyquantitative yield in 20 hrs. Coagulation of the latex produced a plastic, coherent polymer whichwas soluble in" acetone. when the polymer was.

tested in a tire tread recipe, 8. vulcanizateexhibiting a maximumtensile strength 015600 lbs/in. and an elongation of 675% was produced. Repetitions' 01' the above experiment in the absenceiota modifier produced a polymer which was non plas+ Manon-coherent. and which was only. 1% soluble I The vulcanizates prepared from the unmodified polymerhad maximum tensile strengths from 1000 to- 2000-,1bs./in. less-{than those produced trom'the modified polymenand elongations only about half as great. Whenthe in. acetone.

modified polymer was compared further with'the unmodified polymer, it was found thatthe modigfled polymer was much'easie'r to work on the mill. and the dispersion of pigments inthemodified polymer was considerably better. Other modifiers such as bis(ethoxythiono) trithiocarbonate and bis(tetrahydrofurfuryioxythiono'l trithiocarbonate maybe employed as the modifier with equivalentresults. in whibhthe modifier is in.-

upon the properties desired i'n the product, the higher proportions of modifier in general ,producing softer. more soluble polymers. Very small amounts of modifier such as 0.1% ort'even;.less based on the monomersin the emulsion may pro- .i'o undly" affect the nature 'of duced, and amountsuptofiq'e or more rnayadvantageouslybe employed. It'inay also be admixture 0! trithiocarbonate modifiers with each other or with other known dialkyl dixanthogens, tetraalkyl thiuram polysulfides, mercaptoalkylthiazoles or other types of compounds known to exhibit modifying activity in emulsion polymerization.

I'he modifying agents oi this invention may be employed in the polymerization in the form oi an aqueous emulsion of butadiene-Lii hydrocarbons,

the polymer proby which is meant butadiene-lfi (commonly termed butadiene) and its homologue! which enter into olymerization reactions in essentially the same manner such as isoprene, 2,3-dimethylbutadiene, either alone or in admixture with each other and/or other monomers copolymerizable therewith such as styrene, isobutyaqueo lene, acrylonitrile, methyl methacrylate, methyl acrylate, methyl vinyl'ether, methyl vinyl ketone, and other unsaturated esters, ethers, and ketones. For the production oi rubbery products, these other monomers should gieegemployed in an amount smaller than the buta- The polymerization of the above materials in aqueous emulsion may be eiiected by various initiators of polymerization such as per-compounds including per-acids, peroxides, and per-salts such as persuliates, perborates, percarbonates, and the like as well as other typesoi initiators such as diazoaminobenzene, bisultltes, hydrosuliltes, and

dipotassium diazomethane disulfonate.

The polymerization reactions may b catalysed in any desired manner, the use of heavy metal catalysts being particularly desirable. The heavy metal catalyst may be added to the emulsion in the form oi. less than 0.1% based on the weight ol'the monomers of a simple ionizuble heavy met'-.

al salt such as cobalt chloride, nickelous sulfate. mercuric chloride, etc. as disclosed in the copendmg application of William D. Stewart, Serial No. 379,712 flied February 14, 1941, or in the form 0! a redox system comprising a heavy metalvand a material such as sodium pyrophosphate, levulinic acid, glycine, cystine. beta-mercaptoethsnol, quebrachitol, ox-bile or cholesterol as disclosed in the copending application of William D. Stewart, Serial Nos. 379,713 to 379,717 flied February 14, 1941.

Any of the emulsifying agents known to be' useful in connection with the emulsion polymerization of butadiene hydrocarbons may be employed. The polymerlzationsmay be effected under acid conditions by employing as emulsifying agents salts oi organic bases containing long carbon chains such as the hydrochloride of diethylaminoethyloleylamide, the hydrochloride oi the and scope oi the invention as deilned in thempende'dclaims.

Iclaim: 1. The method which com rises m y riains a butadiene-Ld hydrocarbon in the form of an I emulsion'inthepresenceotasmall amoun of a compound containing the group slide.

wherein. x is a member of the group consisting sion, in the presence of bis(isopropoxythiono) trithiocarbonste.

4. The method which comprises polymerizing in the iormotanaqueousemulsion amixturcoibutadiene and a smaller amount oi a monomer copolymerisable therewith in aqueous emulsion, in

"thepresenoeoiasmallamountoiacompound inthepresenceoia 'containingthegrmip.

- s x s --.x-4.':-s-8-s-&-x wherein Z isa member. of the group consisting oi oxygen and sulfur. a

5.- The method which comprises polymerizin a mixture of butadieiie and a smaller amount of acrylonitrile in the form of an aqueous emulsion bis(alkolythlonol 'trithiocarbonate.

' o. The method .whioh'comprises polymerizing a mixture or butadicne and a smaller amountof acrylonitrile in the form of an aqueous emulsion in thepresence o! bis(o) trithiodiethylaminothoxyanilide of oleic acid, trimethylcetylammonium sulfate, etc., under alkaline conditions by employing soaps such as sodium 'oleate, sodium myrlstate, potassium palmitate, etc., and under-acid, alkaline or neutral conditions by employing synthetic saponaceous materials suchas hymolal suli'ates or alkaryl sultonates including sodium lauryl sulfate, sodium lsobutyl naphthalene sulionate, -etc.-

Although I have herein disclosed specific embodiments of my invention, I do not intend to limit the invention solely thereto, -ior it will be obvioustothoseskilledintheartthatmany bonamvariations and modiflcationsarewithin thespirit carbonate.

'7. The-method which comprises polymerizing a mixture oi'butadiene and a smaller amount of acrylonitrile in the i'orm of an aqueous emulsion in the'presence oi a compound containing the s x: s wlines wherein xisamemberoi'the groupconslsting of oxygen and suliur.

8. The method which comprises polymerizing a mixture oi butadie'ne anda smaller amoimt of styreneintheformoianadueousemulsionin the presence or a bis(alkox:thion0) trithiocar wamo n smou.

polymerizing. 

